1. Field of the Invention
The invention relates to an axial support of a winding drum in a hoisting apparatus comprising a frame, a grooved winding drum supported substantially perpendicular to its longitudinal axis against the frame by bearings, a hoisting rope and machinery, the winding drum comprising at least one axial support element close to the circumference of the winding drum and the frame comprising at least one axial support element close to the circumference of the winding drum.
2. Description of the Prior Art
A hoisting apparatus intended for moving a load vertically is usually a part of either a fixed rope hoist or a rope hoist which can be moved along a track by means of a trolley. The hoisting apparatus can also be used as such for hoisting a load. The hoisting apparatus comprises a winding drum which, by utilizing rotating motion, winds a hoisting rope used as hoisting means on or off the winding drum, whereby the position of the load fastened to the hoisting rope by means of a hook can be controlled in respect of the hoisting apparatus. On the surface of the winding drum there is a groove with a pitch, and when the winding drum rotates, the hoisting rope is guided to this groove. The winding drum is typically rotated by machinery which consists of a motor and a gear. The winding drum is supported by bearings to the frame of the hoisting apparatus. The purpose of this support is to expose the frame of the hoisting apparatus to rope force caused by the load. Rope force can be divided into two main components. The stronger one of the components, i.e. a vertical component, has a perpendicular effect in respect of the longitudinal axis of the winding drum and the weaker component, i.e. an axial component, is parallel to the longitudinal axis of the winding drum. The axial component of the rope force is caused by the angle formed by the hoisting rope and the longitudinal axis of the winding drum. The axial component of the rope force causes that in the direction of its longitudinal direction, the winding drum is eccentric in respect of the frame of the hoisting apparatus, which additionally stresses the bearings of the winding drum and complicates the optimization of the bearing structures of the rope hoist.
A known solution to support a winding drum axially, i.e. in the direction of the longitudinal axis of the winding drum, is to provide the winding drum with a central axis by which the winding drum is axially pivoted by a bearing supporting the load at least from one end of the winding drum to the frame of the hoisting apparatus. According to the solution, the central axis is provided with ball bearings, and retaining rings and a collar of the axis are used for locking the winding drum in the direction of its longitudinal axis. The problem is, however, that because of the bearings at least one end of the winding drum is closed, wherefore the interior of the hollow winding drum cannot be efficiently utilized and, for example, the machinery cannot be placed inside the winding drum.
Another known solution to support the winding drum axially is to form a bearing surface onto the frame of the hoisting apparatus, the bearing surface being placed against the end surface of the winding drum. The problem of this solution is that it requires more space in the longitudinal direction of the winding drum and that it is difficult to check and replace the bearing surface. This type of support is known from the publications DE-816737 and DE800246, for example.
The publications DE-261238 and SE-38386 disclose a hoist comprising a winding drum at both ends of which there is a protrusion on the outer circumference of the winding drum, the protrusion extending round the entire circumference of the winding drum and forming one edge for the space intended for bearing balls of the winding drum. The other edge for the space intended for bearing balls is formed by a ring in connection with the frame and extending round the entire circumference of the winding drum. In these publications, the axial movement of the winding drum is restricted by the protrusion on the outer circumference of the winding drum, the bearings of the winding drum and the ring in connection with the frame. A drawback of the solution is, for example, that the elements implementing the axial support for the winding drum have to extend round the entire circumference of the winding drum, which increases the costs of the solution. Furthermore, since the bearings of the winding drum are a part of the axial support of the winding drum, the rotational movement of the winding drum is impaired and the bearings may become damaged.
It is an object of the present invention to provide a simple axial support for a winding drum, the support being easy to make.
According to the invention, the axial support of the winding drum in the hoisting apparatus is characterized in that at least one axial support element of the winding drum or at least one axial support element of the frame is discontinuous in the circumferential direction of the winding drum and that the axial support element of the winding drum and the axial support element of the frame are arranged in respect of each other such that the movement of the winding drum in the direction of its longitudinal axis, which is caused by an axial component of the rope force of the hoisting rope, is hindered at least in one direction.
The essential idea of the invention is that in a hoisting apparatus intended for moving a load vertically and comprising a frame, a grooved winding drum supported to the frame by bearings substantially perpendicular to the longitudinal axis of the winding drum, a hoisting rope and machinery, the movement of the winding drum in the direction of the longitudinal axis, which is caused by the axial component, i.e. the component parallel to the longitudinal axis of the winding drum, of the rope force of the hoisting rope, is hindered at least in one direction such that there is at least one axial support element close to the circumference of the winding drum and that there is at least one axial support element in the frame, close to the circumference of the winding drum, and at least either the axial support element of the winding drum or the axial support element of the frame substantially extends round the circumference of the winding drum, and that the axial support element of the winding drum and the axial support element of the frame are arranged in respect of each other such that the winding drum cannot move in the direction of its longitudinal axis. According to a preferred embodiment of the invention, the axial support element of the winding drum is placed onto the outer surface of the winding drum. According to another preferred embodiment of the invention, the axial support element of the frame is arranged in the circumferential direction of the winding drum substantially at the same level at which the hoisting rope comes into contact with the winding drum, when it either leaves or reaches the winding drum. According to a third preferred embodiment of the invention, the length of either the axial support element of the winding drum or the axial support element of the frame in the circumferential direction of the winding drum is substantially shorter than the length of the winding drum circumference.
The invention provides the advantage that the axial support of the winding drum has a simple structure which is easy to check and service. Furthermore, the structure does not require space outside the winding drum in the longitudinal direction. When the axial support element of the winding drum is placed at such a place on the outer surface of the winding drum where grooves for the rope cannot be made, the axial support element does not affect the length of the winding drum either. By placing the axial support element of the winding drum onto the inner surface of the winding drum, the length of the winding drum can be minimized. When the axial support element of the frame is arranged in the circumferential direction of the winding drum-at the same level at which the hoisting rope comes into contact with the winding drum, when either leaving or reaching the winding drum, the frame of the hoisting apparatus can be directly subjected to the axial component of the rope force. When the length of either the axial support element of the winding drum or the axial support element of the frame is substantially shorter in the circumferential direction of the winding drum than the length of the winding drum circumference, the axial support element can be checked and replaced easily. By arranging one or more axial support elements of the winding drum at both ends of the winding drum and forming axial support elements at the frame, corresponding to the axial support elements of the winding drum, the forces caused by the axial component of the rope force of the hoisting rope can be distributed more evenly to the frame, which further makes it possible to optimize the supporting structures of the rope hoist.
Further scope of the applicability of the present invention will become apparent from the detailed desription given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.